To waterproof a dining table, sand the surface until smooth and remove all old paint. Then, seal it with a coat of outdoor wood paint and at least 3 coats of sealant, such as polyurethane, until it's as smooth as you want. First, choose a paint that is made for outdoor use and that is suitable for furniture. Then, clean the furniture of any dirt and sand it lightly to create a better finish bond.
Wipe off any remaining dust with the adhesive cloth. Then, with gloves, paint all surfaces that may be exposed to the weather. Store the drying piece inside for a few days or a few weeks for better results. Sealing is the key to having outdoor furniture.
Seal to the last surface and crevice, including the bottom of the part, including the soles of the feet. We use Sherwin Williams water-based polyurethane. Since it was white paint, we were recommended to use water-based paint, since it is milkier and does not have the usual yellow tint. Apply a minimum of three coats for adequate protection.
A covered porch or patio is an ideal place to place indoor furniture, as the furniture will have some protection from the elements. When I approached the furniture section, I could see four white farmhouse table legs protruding into the air. So if you're thinking of using a wooden dining table outside and don't have a covered patio, simply cover the table when needed and it'll last for years.